The invention relates to a rear differential gear lock controller of a vehicle.
A conventional rear differential gear lock controller is known which allows a rear differential gear to be locked by a differential gear lock switch at speeds less than a set vehicle speed and prohibits the rear differential gear from being locked at speeds greater than or equal to the set vehicle speed. However, this type of conventional controller encounters breakage and failure of a speed sensor. Once the speed sensor detects no speed pulse (hereinafter referred to as "speed sensor failure" where applicable), the speed sensor erroneously judges that the vehicle is running at speeds less than the set vehicle speed even if the vehicle is running at speeds greater than or equal to the set vehicle speed. As a result, the rear differential gear is allowed to be locked by the differential gear lock switch.
As described above, the conventional rear differential gear lock controller erroneously judges, upon occurrence of a speed sensor failure, that the vehicle is running at speeds less than the set speed when making a turn even if the vehicle is actually running at speeds greater than or equal to the set speed. As a result, the differential gear lock switch has been turned on, and the rear differential gear is locked, hence causing problems, such as damaging the rear differential gear lock mechanism or causing a sharp under-steering due to the locking of the rear differential gear.